Predatory stress induces hippocampal cell death by apoptosis in rats

It is commonly accepted that stress may induce brain damage, especially in hippocampal formation, but the mechanisms that cause such damage are not well understood. This paper investigated the impacts of predatory stress on the hippocampus using cat-exposure to rats. The rats were divided randomly into single stress, 2-, 4-week stress and control group. ISEL and electronic microscope were employed to confirm the occurrence of apoptosis in hippocampus. Our results showed that repeated predatory stresses may result in a pattern of intensive behavioral and endocrinal responses, and lead to the neuronal cell loss in hippocampus. ISEL results displayed that there are some ISEL-positive cells with characteristic apoptotic ultrastructural changes found most in hippocampal CA3 and CA1 in the repeated stressed rats. These results indicate that apoptosis may be one of the most important neuropathological mechanisms for cell loss or hippocampal atrophy induced by predatory stress. Meanwhile, significant positive correlation between serum cortisol level and the number of apoptotic cells in CA3 supports that excessive GCs due to predatory stress, is associated with hippocampal cell apoptosis.